Posted: 13/07/2015 at 18:44
It sounds like they will be caterpillars. What kind I do not know without a pic, many plants, especially perennials, can tolerate substantial leaf damage, so a few leaf-feeding caterpillars should not be a concern. Handpicking and natural enemies will provide sufficient control.
General predators include birds, assassin bugs, lacewings, predaceous ground beetles, parasitic wasps or flies and spiders. Naturally occurring diseases caused by viruses, bacteria, and fungi often kill caterpillars as well. Consider insecticides only when damage is becoming intolerable and as a last resort. You will probably find signs that the predators are at work and the damage will be short lived.